Silicon and aluminum, after oxygen, are the most abundant elements on earth. Their oxides are stable, relatively inert and cheap. Because of this, these oxides have found many applications, for example as support material in catalysis or in chemical analysis. Many of these applications require tailoring of the surface properties.
Silica glasses, for example, are an important class of materials because of their excellent optical properties. The specific properties of a silica glass depend on its composition and fabrication method.1 Whereas silica glasses made from natural quartz show considerable absorption above 200 nm, synthetic fused silica is transparent at wavelengths down to 180 nm. Optical transparency is a desired property in the field of biosensing, where techniques of fluorescent labeling are well-developed.2 For biosensing, the material of choice should also be easily functionalizable.
For silica, a number of functionalization methods have been developed, such as for example esterification of silica surface hydroxyl groups with alcohols.3 However, a disadvantage of this method is that the resulting monolayers are prone to hydrolysis, which may be problematic for certain applications.4 
The currently prevailing method makes use of organosilanes such as organotrichloro- or organotrialkoxysilane derivatives,5 which can react with surface hydroxyl groups to yield a closely packed monolayer.6, 7 For example US 2005/0255514, incorporated by reference herein, discloses a method to functionalize substrates such as silicon, glass, silica, quartz and metal oxides with a silane having an oligoethylene oxide group to provide protein resistance. In general, modification of OH-terminated surfaces with organosilanes is rapid, is usually performed in dilute solutions, and several functional groups are compatible with the procedure. Patterned functionalization of silica surfaces is e.g. possible using soft lithographic techniques.7 However, the reaction is notoriously difficult to control due to the tendency of silanes to condense in solution.8, 9 In addition, the high reactivity of organotrichlorosilanes requires careful handling and limits their use in an industrial environment. Thirdly, the monolayer is only stable in a relatively small range of conditions10 and is prone to hydrolysis.
In Langmuir 22, 8359-8365 (2006), incorporated by reference herein, Mischki et al. compared the photochemical and thermal reaction of alkenes with both H-terminated and OH-terminated silicon surfaces.11 The photochemical reaction of 1-decene with silicon oxide-covered silicon at a wavelength of 300 nm is disclosed. However, this reaction leads to surfaces with a lower hydrophobicity (contact angle of 59°), a lower coverage, and a lower reaction rate as compared to the thermal reaction of the OH-terminated surface (contact angle of 91°). Reaction of the H-terminated surfaces with 1-decene resulted in surfaces with a comparable hydrophobicity for both the thermal and the photochemical reaction (contact angle of 102° in both cases), but the coverage of the surface and the reaction rate were higher for the thermal reaction.
Several methods for the modification of metal surfaces are known from prior art. For example US 2002/0018854, incorporated by reference herein, discloses a method for the modification of an OH-terminated metal surface using hydridosilanes. The modification reaction can be performed in the vapor phase, in the liquid phase, in supercritical fluids, in dilute or concentrated solutions, and at high or low temperatures. Examples include the surface modification of titanium, stainless steel, nickel and tin.
Recently, Raman et al. disclosed in Langmuir, 23, 2284-2288 (2007), incorporated by reference herein, a method for the surface modification of stainless steel, the method comprising the formation of self-assembled monolayers of long alkyl chain carboxylic acids with different terminal groups on the native oxide layer of stainless steel 316L via a solution-deposition method. The monolayers formed were chemically and mechanically stable. Static contact angles varied from 38° to 42° for the surfaces modified with acids comprising a hydrophilic terminal functional group, whereas the surface modified with octadecylcarboxylic acid showed a static contact angle of 104°.
For alumina, no method is available yet that yields hydrolytically stable monolayers. For these and the other specified metal oxide surfaces no photochemical method to attach high-quality organic monolayers is reported.